Construction method of large-span cable-stayed bridge epoxy steel strand stay cable

Abstract

The application relates to a construction method of an epoxy steel strand cable-stayed cable of a large-span cable-stayed bridge, and belongs to the field of bridge cable construction. In the method, when a single cable is hung, the steel strand is led upwards from a bridge deck (or an upper cross beam), is lowered into a tower through a tower top high-tower cable-through machine, passes through a tensioning end anchorage device, reaches a tower outer cable guide pipe orifice, is then passed downwards through a main beam fixed end anchorage device from an HDPE pipe, the tower beam two ends are respectively tightly clamped, then a single tensioning jack is installed to perform tensioning pre-tightening, after tensioning is completed, the next cycle is continued. The cables are installed one by one in the order from top to bottom and from outside to inside, the single tensioning is performed by using an equivalent tensioning method, and until the cable hanging work is completed. The construction efficiency and accuracy are greatly improved, the installation precision, installation quality and installation speed of the cable-stayed cable are ensured, and good economic benefits and social benefits are obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of bridge engineering, in particular to a construction method of a cable-stayed cable of a cable-stayed bridge. BACKGROUND

[0002] Steel strand cable is a kind of cable structure commonly used in modern cable-stayed bridge cable, which has been widely used in Europe and the United States, Japan and other countries. The biggest advantage of steel strand cable is that the installation and tensioning process of the cable is simple, the construction is convenient, the whole cable can be transported by strand, and the water and land transportation is not limited. In the construction, the steel strand cable mostly adopts the construction process of circulating cable by winch, single tensioning and overall cable adjustment. In the process of continuous development of bridge steel strand cable technology, it also has the advantage of single replacement of steel strand. Due to the above obvious advantages, steel strand cable is also widely used in the construction of domestic long-span cable-stayed bridges. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a construction method of a cable-stayed cable of a cable-stayed bridge. The tower top support is built, the winch and the high tower cable machine are installed on the tower top support, the continuous cable of the strand is carried out, the strand is pulled up and then passed through the (HDPE) outer sleeve from top to bottom, the clamping pieces are tightened at both ends of the tower beam, and the whole strand of each cable-stayed cable is tensioned (one tension) by the equivalent tensioning method, and then the whole bundle is tensioned (two tensions) after the single tensioning is completed. The next cycle is continued. The cable-stayed cables are installed in the order of from top to bottom and from outside to inside, until the cable hanging work of all cable-stayed cables is completed.

[0004] The cable-stayed cable hanging construction method of the present application greatly improves the construction efficiency and accuracy, ensures the installation accuracy, installation quality and installation speed of the cable-stayed cable, and aims to obtain good economic benefits and social benefits.

[0005] The technical scheme adopted by the present application is: a construction method of an epoxy steel strand cable of a long-span cable-stayed bridge, comprising

[0006] Step one, construction preparation: including the construction of beam end platform, tower outer platform, tower inner platform and tower top support, wherein the high tower cable machine and the winch are arranged on the tower top support, the traction steel wire rope is pre-wound on the high tower cable machine reel, one end of the steel wire rope is lowered to the tower end anchor, and the other end is lowered to the tower lower steel strand placement, and is connected with the first lengthened steel strand;

[0007] Step two, steel strand unloading:

[0008] After the unloading length of each steel strand is completed, the sleeve of each steel strand is exposed to expose the steel wire, the two ends of the adjacent two unloaded steel strands are connected, and the whole coil of steel strand is stored in a fixed position.

[0009] Step three, (HDPE) outer sleeve splicing

[0010] The (HDPE) outer sleeve is spliced to the required design length of each cable, the (HDPE) outer sleeve is connected with the waterproof cover to form a whole, and the (HDPE) outer sleeve is connected with the waterproof cover to form a whole.

[0011] Step four, anchor installation

[0012] After the anchor at both ends of the tower beam is assembled and verified to be correct, the anchor is temporarily fixed on the anchor pad;

[0013] Step five, installation of multi-hole counterforce frame

[0014] The multi-hole counterforce frame includes a pressure plate, a support column and a support plate, the pressure plate is supported on the support plate through the support column, the multi-hole counterforce frame is installed at the tail of the anchor plate of the tower end anchor, the support plate is connected with the anchor plate, and the pressure plate is spaced from the anchor plate. Adjust the installation of the multi-hole counterforce frame and the anchor plate to make the hole arrangement on the pressure plate consistent with the hole arrangement of the anchor plate;

[0015] Step six, (HDPE) outer sleeve hoisting

[0016] Before threading the cable, the (HDPE) outer sleeve is hoisted to the pre-buried pipe at the tower end, and the two ends thereof are temporarily fixed with the tower and the beam respectively. In the process, the cable threading machine is started until the two ends of the first lengthened steel strand are respectively drawn into the tower end anchor and the beam end anchor and fixed. The lengthened steel strand passes through the (HDPE) outer sleeve, and the (HDPE) outer sleeve supported thereon is straightened by tensioning the lengthened steel strand;

[0017] Step seven, single steel strand threading and tensioning

[0018] 7.1 Single threading of high tower cable threading machine

[0019] The steel strand wound in step two is placed on the cable laying disc under the tower, the first steel strand is drawn, the cable laying disc is rotated, and the steel strand is drawn to the top of the tower by the high tower cable threading machine. The single steel strand passes through the high tower cable threading machine, and then is sequentially threaded from the top of the tower → the inner cavity of the tower → the tower end anchor → the pre-buried pipe in the tower end → the (HDPE) outer sleeve outside the tower → the beam surface by using the weight of the steel strand. The front and rear steel strands are connected end to end to realize continuous threading. After the front steel strand is anchored in the beam end anchor at the beam end, the front and rear steel strands are disconnected at the tower end. Then the front steel strand is tensioned, and after the front steel strand is tensioned, the rear steel strand is sequentially threaded from the tower end anchor;

[0020] 7.2 Single steel strand tensioning

[0021] Tension each strand wire one by one, and tension each strand wire according to more than 90% of the tension force, and use the electric algorithm to calculate the tension force value of each strand wire, and the remaining tension force is used as the average cable force. After the tension of all the strand wires of each cable is completed, the uniformity of the cable force of each strand wire is checked, and the cable force is adjusted according to the remaining tension force, so that the tension force of all the strand wires reaches the average;

[0022] Repeat steps 7.1 and 7.2 to complete the cable threading and tensioning of all the strand wires of one cable;

[0023] Step eight, secondary tensioning

[0024] After the single tensioning of all the strand wires of one cable in step seven is completed, the entire bundle of strand wires of the cable is tensioned, and the secondary tensioning is carried out in stages until the tension reaches 100%. After the tensioning is completed, the exposed strand wires at the tower end and the beam end are protected to avoid exposure.

[0025] Step nine, clamping and pressing

[0026] For low-stress anchoring of the cable, in order to ensure the reliability of the anchoring, after the cable force adjustment is completed, the single strand wire with a cable force less than 0.4σ con is subjected to clamping and pressing operation. The clamping and pressing of the strand wire is carried out by using a pressing jack.

[0027] As a preferred operation of the above method: in step one, one end of the steel wire rope is lowered from the tower top manhole to the tower end anchor, and the other end is lowered from the pre-installed pipe outside the tower wall to the steel strand wire placement below the tower, and is connected with the first lengthened steel strand wire. When the steel strand wire is pulled, the steel strand wire rises to the high tower cable threading machine through the pipe (PE pipe, which is used to protect the strand wire and avoid damage due to friction during pulling).

[0028] As a preferred operation of the above method: in step two, the steel strand wire is unwound on the pay-off stand, and the steel strand wire is supported by the roller. After the sheath of each steel strand wire is stripped, the center wire is upset. The two adjacent unwound steel strand wires are connected by wire binding, and the entire coil of steel strand wire is protected during storage.

[0029] As the preferred operation of the above method: in step four, the tower end anchor device includes an anchor plate, a support cylinder, a nut and a tension end sealing cylinder, the anchor plate is located at the tail end of the support cylinder, the nut is screwed on the outside of the support cylinder, the support cylinder is supported on the anchor pad, and the nut is tightly attached to the anchor pad; the beam end anchor device includes an anchor plate, a fixed end sealing cylinder and a grommet, the grommet is located at the tail of the fixed end sealing cylinder and is welded as a whole with the fixed end sealing cylinder, a water drain groove is arranged on the side of the grommet close to the anchor pad, the water drain groove is located below the grommet, and the side of the grommet where the water drain groove is located is tightly attached to the anchor pad; before the cable hanging construction, the anchor device is fixed on the anchor plate in advance, and after the nut or the grommet is tightly attached to the anchor pad, the anchor device is temporarily fixed on the anchor pad.

[0030] As the preferred operation of the above method: in step six, the (HDPE) outer sleeve pipe is passed through the extension pipe and extends a certain length; the temporary hoop is used to clamp the front and rear ends of the extension pipe; the HDPE outer sleeve pipe is erected by using the roller frame and the sleeper to prevent damage to the HDPE outer sleeve pipe during movement; the (HDPE) outer sleeve pipe is hoisted by using the tower crane, the (HDPE) outer sleeve pipe is hoisted in advance to the bridge deck by the tower crane, and then is hung on the tower outer hoisting point after conversion by using the hand-operated hoist, the lengthened steel strand is respectively drawn into the tower end anchor device and the beam end anchor device, and the clamping piece is installed in the anchor hole of the anchor device to fix the lengthened steel strand, and the lengthened steel strand is straightened by tensioning, thereby supporting the (HDPE) outer sleeve pipe.

[0031] As the preferred operation of the above method: in step seven, in step 7.1, when the steel strand passes through the tower embedded pipe opening, the pipe (the pipe is used as a guide pipe between the anchor hole on the pressure bearing plate of the multi-hole counterforce frame and the anchor hole on the anchor plate of the tower end anchor device) is used to guide the steel strand into the cable guide pipe through the tower end anchor device, the electric hanging basket is used as a construction platform at the outlet of the tower outer cable guide pipe to manually assist the HDPE outer sleeve pipe to pass through, and when reaching the beam end anchor device, the steel strand is passed into the beam end anchor device by using the traction rope.

[0032] As the preferred operation of the above method: in step seven, in step 7.1, during the process of passing the steel strand, the pipe opening of the beam end cable guide pipe and the port of the (HDPE) outer sleeve pipe end waterproof cover are wrapped with a hose (that is, the pipe opening through which the steel strand passes is wrapped to prevent scratching); at the same time, when the number of steel strands passing through the cable is more than half, the steel strands that have completed the cable passing are bundled, and the ends of the steel strands that are being passed are bundled to prevent crossing during the cable passing process.

[0033] As a preferred operation of the above construction method: In step seven, in step 7.1, during the lowering of the steel strand, a measuring device is set up to calculate the lowering length of the steel strand in order to control the start and stop of the high tower cable threading machine. A metering sensor is fixedly installed on the support of the high tower cable threading machine, and multiple sensing points are set on the circumference of the drum used for cable lowering of the high tower cable threading machine. During the process of the drum rotating and lowering the cable, the multiple sensing points periodically sense the metering sensor during its circumferential stroke. The metering sensor is connected to the control cabinet to calculate the cable lowering length. The construction personnel control the speed and start and stop of the high tower cable threading machine according to the cable lowering length.

[0034] As a preferred operation of the above construction method: In step seven, in step 7.2, in order to monitor the change of cable force of the steel strands during the tensioning of each steel strand and to verify the tensioning accuracy, a sensor is installed during construction to monitor the change of cable force of the first steel strand during the tensioning process of the subsequent steel strands. The readings of the sensor installed on the first steel strand are recorded and compared with the tensioning calculation value calculated by the computer at the same time, so as to realize the dual control of the calculation and the actual tensioning process.

[0035] To check the uniformity of cable tension, after the individual tensioning of all the strands of a stay cable is completed, several strands at different positions in the same bundle are selected and pulled out using jacks to obtain the hydraulic pressure value corresponding to the cable tension. If the force value exceeds the error range, the cable tension of each strand is averaged according to the remaining tension value.

[0036] As a preferred operation of the above construction method: In step seven, specifically in step 7.2, the tensioning of a single steel strand is performed at the tower end. The steps are as follows:

[0037] a. Pass the top pressure rod through the steel strand and the perforated reaction frame, and put the top pressure sleeve on the top pressure rod;

[0038] b. Pass the single-hole jack through the steel strand and press it against the top pressure sleeve to ensure that the groove of the jack piston head is fully embedded in the top pressure sleeve, i.e., the initial state is in place;

[0039] c. Start the oil pump and use an electric algorithm to calculate the force value of each steel strand according to 90% of the tension force for tensioning. The remaining 10% of the tension force is used as the average cable force.

[0040] d. When the tension reaches the calculated tension, stabilize the oil pressure and stop tensioning. Observe the scale on the jack or use a steel ruler to measure the piston stroke and record the value.

[0041] e. Based on the recorded data, calculate the elongation of the steel strand and compare it with the theoretical value to see if it meets the allowable deviation. If it is within the deviation range, continue construction; otherwise, stop tensioning and check the cause.

[0042] f. At the same time, observe whether the cable force value on the sensor matches the tension force. The cable force dispersion of a single strand should be within ±2%. If it exceeds the design allowable range, the cable force should be averaged and tensioned again according to the remaining 10% force value until the last steel strand is tensioned. When the sensor reading is within the allowable range of the design value, the cable force error of the whole bundle should be within ±5%.

[0043] g. After all strands are tensioned, remove the single-hole anchor and sensor on the first strand, install the working clamp, and re-tension it with a single-hole jack so that the tensioning anchor force of the first strand is consistent with the reading of the last strand.

[0044] Compared with the prior art, the advantages of the present invention are as follows:

[0045] The construction method for installing epoxy steel strand stay cables in long-span cable-stayed bridges has the following characteristics:

[0046] 1. A tower top support is installed at the top of the cable-stayed bridge tower, and a high-tower cable threading machine is installed on the tower top support to provide traction power to pull a single steel strand from the bottom of the tower to the top of the tower. The single steel strand passes through the wire splitting wheel group of the high-tower cable threading machine and uses its own weight to pass down along the HDPE outer tube to the bridge deck, completing the cable threading process.

[0047] 2. For steel-concrete composite girder cable-stayed bridges, the bridge deck has not yet been laid when the stay cables are installed. When using traditional winches to circulate the cables, the interface of the bridge deck winch layout needs to be considered. However, the cable-threading method of high-tower cable threading machines does not need to consider the bridge deck construction interface.

[0048] 3. Utilizing an automated cable threading device, the steel strands are threaded using a high-tower cable threading machine, allowing the threading device to be deployed in one go, saving installation time and greatly improving cable hanging efficiency. This avoids the complexity of the traditional winch-based cable threading system, which involves arranging a cyclical cable threading system for each cable number.

[0049] 4. The cable threading machine is used. The power of the cable threading machine and the steel strands slide freely down the HDPE outer tube under their own weight, without tangling. The cable threading speed is very fast. The efficiency is more obvious for cable threading of length greater than 100 meters. It is suitable for the installation and construction of large-span cable stays. Attached Figure Description

[0050] Figure 1 This is a flowchart of the construction method described in an embodiment of the present invention;

[0051] Figure 2 This is a schematic diagram of the cable-stayed bridge construction in an embodiment of the present invention. In the diagram, 1 is the tower top support, 2 is the high tower cable threading machine, 3 is the steel strand, 4 is the cable laying frame, 5 is the steel anchor beam, 6 is the suspended platform, 7 is the HDPE outer casing, 8 is the upper crossbeam, 9 is the main tower, and 10 is the main beam.

[0052] Figure 3The structural schematic diagram of the tower end anchorage in the embodiment of the present application is shown in the figure.

[0053] Figure 4 The structural schematic diagram of the beam end anchorage in the embodiment of the present application is shown in the figure.

[0054] Figure 5 The structural schematic diagram of the porous counterforce frame in the embodiment of the present application is shown in the figure.

[0055] Figure 6 The single cable threading construction flow chart of the high tower cable threading machine in the embodiment of the present application is shown in the figure.

[0056] Figure 7 The tensioning schematic diagram of the single steel strand in the embodiment of the present application is shown in the figure, in which 18 is a single-hole jack, 19 is a single-hole anchor, and 20 is a sensor.

[0057] Figure 8 The schematic diagram of the secondary tensioning (overall tensioning) in the embodiment of the present application is shown in the figure, in which 21 is a hollow tension rod, 22 is a tension rod nut, 23 is a variable-diameter sleeve, 24 is a supporting leg, and 25 is a jack.

[0058] Figure 9 The clamping piece pressing schematic diagram in the embodiment of the present application is shown in the figure, in which 26 is a pressing jack. DETAILED DESCRIPTION

[0059] The present application will be further described in detail below with reference to the accompanying drawings, and the embodiments are exemplary and are intended to explain the present application, but should not be understood as a limitation on the present application. The textual description in the embodiments is corresponding to the drawings, and the description of the orientation is also based on the description of the drawings, and should not be understood as a limitation on the protection scope of the present application.

[0060] The present embodiment relates to a cable hanging construction method of an epoxy steel strand cable of a long-span cable-stayed bridge, a construction process and operation points.

[0061] 1. Construction process

[0062] Construction preparation → steel strand cutting, HDPE pipe welding → high tower cable threading machine installation → anchorage installation → HDPE pipe hoisting → single cable threading and tensioning (equivalent tensioning method) → secondary tensioning → clamping piece pressing → temporary protection → full bridge closure → cable adjustment → installation of auxiliary components and cable protection.

[0063] 2. Operation points

[0064] 2.1. Construction preparation

[0065] The construction preparation work mainly includes: equipment preparation, personnel preparation, construction platform and construction channel erection.

[0066] ① Beam end platform: adopt movable independent platform, adopt angle steel, steel pipe welding, operation platform adopt steel jump board paving.

[0067] ② Tower outside platform: adopt vertical lifting type electric hoist basket.

[0068] ③ Tower inside platform: main tower cable anchor in steel anchor beam, can be in steel anchor beam both sides with steel jump board erection platform.

[0069] ④ Tower top support 1 mainly is to give tower outside platform lifting, tower inside equipment material transportation provides high altitude hoisting point, this support mainly is by pre-buried piece and steel support constitutes, steel support is by main longitudinal beam, crossbeam and diagonal bracing group's portal frame type structure, tower top passage adopts single layer of berle piece and pattern steel plate erection and is formed.

[0070] 2.2 Steel strand unloading

[0071] According to the unloading length formula, calculate the unloading length of each cable number, and pay attention to the following points during unloading:

[0072] ① After unloading each steel strand according to the unloading length, strip the sleeve at both ends of each steel strand strictly according to the stripping length given by the site technician, and use the header machine to header the center wire.

[0073] ② Steel strand unloading is carried out on the pay-off stand (plastic roller). The two adjacent steel strands after unloading are connected by binding with wire, and are coiled on the cable drum until the cable drum is full. Then, the whole coil of steel strand is stored in a fixed position using the site hoisting equipment, and is covered with a rain cloth to prevent surface contamination.

[0074] 2.3 HDPE outer sleeve welding

[0075] Select a suitable welding area on site, and weld each 11m long HDPE pipe to the required length using a hot melt welding machine. The length of HDPE for each cable number is welded according to the length calculated by the technician. Finally, connect the HDPE outer sleeve with the waterproof cover through the HDPE connecting sleeve to form a whole. The strength of the joint position after welding must be higher than that of the base material, and defects such as voids and depressions are not allowed.

[0076] 2.4 High tower cable threading machine positioning

[0077] After the tower top steel support is installed, the high tower cable threading machine and the tower inside hoisting winch are installed in position. Pre-coil the traction steel wire rope on the high tower cable threading machine drum. One end of the steel wire rope is lowered from the tower top manhole to the tower end anchor, and the other end is lowered from the pre-installed pipe in the tower wall to the steel strand placement on the main beam surface, and is connected with the first lengthened steel strand. The function of the pipe is to prevent the steel strand from rubbing against the tower column.

[0078] 2.6 Anchor installation

[0079] After the tower beam end anchor assembly is complete and verified, the anchor is pre-fixed to the anchor pad before the cable construction. After the nut or grommet is tightly attached to the anchor pad, the anchor is temporarily fixed to the anchor pad. The structure of the tower end anchor is as shown in Figure 3 , and the structure of the beam end anchor is as shown in Figure 4 The tower end anchor includes an anchor plate 11, a support cylinder 12, a nut 13, and a tension end sealing cylinder 14. The anchor plate 11 is located at the tail end of the support cylinder 12, the nut 13 is screwed on the outside of the support cylinder 12, the support cylinder 12 is supported on the anchor pad 15, and the nut 13 is tightly attached to the anchor pad 15. The beam end anchor includes an anchor plate 11, a fixed end sealing cylinder 16, and a grommet 17, and an anchor pad 15. The grommet 17 is located at the tail of the fixed end sealing cylinder 16 and is welded as a whole with the fixed end sealing cylinder 16. One side of the grommet 17 is provided with a water drain groove, and the water drain groove is located below the grommet 17. The side of the grommet 17 where the water drain groove is located is tightly attached to the anchor pad 15.

[0080] ①When installing the anchor, ensure that the cable-stayed tower beam anchor hole position corresponds one by one, and the steel strand does not twist or kink after being inserted into the cable;

[0081] ②The grommet 17 of the fixed end (beam end) anchor is provided with a water drain groove on one side. When installing, attention should be paid to the orientation of the water drain groove. The grommet water drain groove should be directly below, and the side of the grommet with the water drain groove should be tightly attached to the anchor pad, so that water can be drained.

[0082] ③When installing the nut, the screwing length of the nut on the anchor plate should be controlled to facilitate the need for overall cable adjustment in the future;

[0083] 2.7 Installation of single-hole tensioning counterforce frame

[0084] The multi-hole counterforce frame 100 is installed on the tower end anchor. The multi-hole counterforce frame support plate is connected to the anchor plate of the tower end anchor, and the hole arrangement of the pressure bearing plate is adjusted to be consistent with the hole arrangement of the anchor plate.

[0085] The multi-hole counterforce frame 100 is divided into multiple types according to the specifications of the anchor. The total height is the same, and it is composed of a pressure bearing plate 101, a support column 102, and a support plate 103 from top to bottom. It plays a role in dispersing steel strands and supporting tensioning counterforce during single strand tensioning.

[0086] 2.8 HDPE outer sleeve hoisting

[0087] Before the cable is inserted, the HDPE outer sleeve needs to be hoisted to the main tower pre-buried pipe and temporarily fixed at both ends to the main tower and the main beam.

[0088] ①Insert the HDPE outer sleeve through the extension pipe and extend a certain length. Use temporary clamps to clamp the front and rear ends of the extension pipe. Use roller frames and sleepers to erect the HDPE outer sleeve to prevent damage to the HDPE outer sleeve during movement;

[0089] (2) HDPE outer sleeve is hoisted by tower crane. The HDPE outer sleeve is hoisted to the bridge deck by the tower crane in advance, and then is hung on the tower outer hoisting point (the next section of cable guide pipe) by the change of hand-operated hoist. The extended steel strand is pulled into the tower anchor and the beam end anchor by the cable threading machine, and the clamping piece is installed for fixation. The HDPE sheath pipe supported by the extended steel strand is straightened by tensioning the extended steel strand.

[0090] 2.9 Steel strand single threading and tensioning

[0091] 2.9.1 High tower cable threading machine single threading

[0092] The processed steel strand is placed on the cable laying disc on the main beam surface. The first steel strand is pulled to rotate the cable laying disc to pull the steel strand from the pipe outside the tower wall to the top of the tower by the power of the cable threading machine. The single steel strand passes through the high tower cable threading machine, and then is sequentially threaded from the tower top to the tower cavity, to the tower end anchor, to the tower embedded pipe, to the outer HDPE pipe, and to the beam surface by the self-weight of the steel strand. The tail of the front steel strand is connected to the head of the rear steel strand, the installation of the whole bundle of steel strands is completed, and the steel strand connection is achieved by locking the pier head part by the connector. In order to prevent the connector from being bent and damaged and falling off when passing through the high tower cable threading machine, a section of protective pipe is sleeved at the head connection, and the both ends of the protective pipe are wrapped with adhesive tape to prevent damage and make the joint pass through the high tower cable threading machine more conveniently.

[0093] When the steel strand passes through the tower embedded pipe, it enters the cable guide pipe through the anchor. The exit of the cable guide pipe outside the tower is used as a construction platform for manual auxiliary threading into the HDPE pipe by using the electric hoist basket. When reaching the beam end cable guide pipe (anchor), the steel strand is pulled out of the beam end anchor by the pulling rope.

[0094] In order to prevent damage caused by the forward or backward movement of the steel strand, the beam end cable guide pipe port and the waterproof cover port are wrapped with a hose. At the same time, when the number of threaded steel strands is more than half, the threaded steel strands are bundled tightly, and the end of the steel strand being threaded is installed with a guide head to prevent crossing during threading.

[0095] The length of the cable strand of the cable-stayed bridge is relatively long, and the threading is continuous by using the high tower cable threading machine. In the process of threading, each steel strand is connected at the head and tail to realize continuous threading of the steel strand. In the construction process, the distance between the tower beam anchor points is large, and the construction personnel control the start and stop of the high tower cable threading machine at the top of the tower. When the steel strand reaches the beam end, the start and stop keys need to be controlled at any time. The length of the steel strand is judged by setting a measuring device to facilitate the construction personnel to control the speed and start and stop of the cable threading machine.

[0096] The metering sensor is arranged on the support of the high tower cable threading machine, 8 sensing points are arranged on the circumferential plane of the drum and the position of the sensor, the sensor is connected to the control cabinet of the cable threading machine, and the cable threading length is output through the metering display screen on the control cabinet. The sensing points on the drum of the cable threading machine record once every time the drum rotates through the metering sensor, and the length recorded each time is 1 / 8 of the circumference of the drum. The circumference of the drum is 5m, and the sensor senses 1 time every 0.625m. The construction personnel can determine the specific length through the value on the display screen.

[0097] 2.9.2 Calculation of single steel strand tension

[0098] 1. Construction control conditions

[0099] In order to ensure that the stress of each steel strand in the single cable meets the design requirements, the cable force error between each steel strand in the cable is not more than ±2% during construction, and the tension is strictly controlled according to the process. The following calculation basis is required for calculating the single tension:

[0100] (1) The installation control tension of the cable-stayed cable is subject to the monitoring instruction;

[0101] (2) The relative displacement amount (or deformation amount) of the cable-stayed cable anchorage point is calculated under the action of the installation control tension of the cable-stayed cable. It is the vertical displacement of the lower anchorage point and the horizontal displacement of the upper anchorage point in the vertical plane where the cable is located. It is temporarily given by the monitoring unit;

[0102] (3) The relevant physical parameters of the corresponding section of the main beam, which are generally determined according to the design;

[0103] (4) The geometric and physical parameters of the cable body.

[0104] 2. Single equivalent tension calculation principle

[0105] In the bridge structure model, the first steel strand is tensioned to the predetermined load, which will cause a new balance state between the bridge deck and the connected components. Corresponding to the applied force, the bridge structure deformation will occur, and the deflection of the steel strand and the HDPE outer sleeve will decrease. When the second steel strand is tensioned, the following situations will mainly occur: due to the increase of the cable force, the deformation of the tower beam structure increases, which leads to the decrease of the cable force on the first steel strand. Due to the influence of the sequence of steel strand tensioning, the tension of the steel strand is different during installation. The tension of the first steel strand is the largest, and the tension of the other steel strands gradually decreases as more steel strands are installed. For example, after the first tensioning, the second tensioning starts. When the second tensioning is loaded, the first tension is decreased. They must have an equal point of cable force, which can be recorded by combining the sensor reading and the oil pump reading.

[0106] 2.9.3 Steel strand single tensioning

[0107] (1) Tension monitoring

[0108] To monitor the cable force change and verify the tension accuracy, sensors are installed during construction. The readings of the sensors installed on the first steel strand are recorded by a dedicated person, and compared with the calculated tension value to achieve double control of the calculation and actual tension process.

[0109] For the test of cable force uniformity, after completing one cable of all steel strands, select 5 steel strands at different positions in the same cable for tension test by jack, and compare the oil pressure value on the precision oil pressure gauge. If there is a difference in the readings, then each strand is tensioned by 10% of the remaining tension value to average the cable force.

[0110] When hanging the cable, the sensor is installed on the first steel strand, and the installation sequence is: gasket-sensor-single-hole tool anchor.

[0111] (2) Single tension operation, as shown in Figure 7

[0112] a. Connect the oil pipe of the oil pump and the jack, check whether the precision pressure gauge is consistent with the jack, and in the unloaded condition, move the two strokes before tensioning to ensure that the jack has no problem during tensioning;

[0113] b. Pass the whole counterforce frame through the steel strand and install it on the anchor;

[0114] c. Pass the pressure rod through the steel strand and the counterforce frame, and put the pressure sleeve on the pressure rod;

[0115] d. Pass the single-hole jack through the steel strand and press it on the pressure sleeve, ensure that the jack piston head groove is fully embedded on the pressure sleeve;

[0116] e. Start the oil pump, calculate the force value of each steel strand according to 90% of the tension force for tensioning, and the remaining 10% for cable force averaging;

[0117] f. When the tension reaches the given tension calculated, stop tensioning and observe the scale on the jack or measure the piston stroke with a steel ruler, and record the value on the table;

[0118] g. According to the data recorded on the table, calculate the elongation of the steel strand and compare it with the theoretical value to see if it meets the specification allowable deviation requirement. If it is within the deviation range, continue construction; otherwise, stop tensioning and check the reason;

[0119] ​h. At the same time, observe whether the cable force value on the sensor is consistent with the tension force, and the dispersion of the force of a single strand is within ±2%. If it exceeds the design tolerance, the remaining 10% force value should be used for average tensioning until the last strand is tensioned to the design value within the allowable range, to ensure that the error of the entire cable force is within ±5%;

[0120] i. Remove the single-hole anchor plate and sensor, install the work clamp, and use the single-hole jack to re-tension it, with the tensioning anchoring force consistent with the last strand reading.

[0121] 2.10 Second tensioning, as shown in Figure 8 .

[0122] According to the main beam construction process, the second tensioning of the cable is carried out according to the monitoring instructions. The second tensioning uses the overall tensioning tool for the entire bundle tensioning, which is achieved by adjusting the nuts on the anchor. The cross-jack is used, and the support foot 24, jack 25, variable diameter sleeve 23, hollow pull rod 21 and pull rod nut 22 are installed. In order to reduce the loss of prestress, the second tensioning is carried out in stages, with 50% tensioning first and then 100% tensioning.

[0123] After the second tensioning is completed, the exposed steel strands at the tower and beam ends need to be closed for temporary protection.

[0124] 2.11 Clamp pressing

[0125] For low-stress anchoring of the cable, in order to ensure the reliability of the anchoring, after the cable force is adjusted, the operation of pressing the clamp is carried out for the single strand with a cable force less than 0.4σ con . The clamp is pressed using a pressing jack, which is a prior art in the field, as shown in Figure 9 .

[0126] 2.12 Steel strand length cutting

[0127] After the main beam closure, the cable force is adjusted according to the monitoring instructions, and after completion, the steel strand is cut according to the reserved length. The length of the steel strand should be compatible with the length of the protective cover, and the length of the entire steel strand should be cut flush, with each length being consistent. Ensure that the length of the entire steel strand is 5-20mm shorter than the protective cover, and not too short to meet the future cable replacement requirements.

[0128] 2.13 Enter the subsequent process

[0129] After the installation of the epoxy steel strand cable is completed, the subsequent auxiliary member installation and corrosion prevention process is entered.

[0130] In addition to the above embodiments, the present application also includes other embodiments, and any technical solutions formed by equivalent transformation or equivalent replacement shall fall within the protection scope of the claims of the present application.

Claims

1. A construction method for epoxy steel strand stay cables of a long-span cable-stayed bridge, characterized in that: include Step 1, Construction Preparation: This includes the construction of the beam end platform, the outer platform of the tower, the inner platform of the tower, and the tower top support. The tower top support is equipped with a high tower cable threading machine and a winch. The traction steel wire rope is pre-wound on the drum of the high tower cable threading machine. One end of the steel wire rope is lowered to the anchor inside the tower, and the other end is connected to the first extended steel wire rope from the lower part of the tower to the place where the steel strand is placed at the bottom of the tower. Step 2: Cutting steel strands: After cutting each steel strand to the required length, strip the steel wires at both ends of each steel strand, connect the ends of two adjacent cut steel strands, and continuously coil them on a cable reel. Then store the entire coil of steel strands in a fixed position. Step 3: Splicing the outer tube The outer sleeve is spliced ​​to the required design length for each cable. For the outer sleeve with a waterproof cover, the outer sleeve and the waterproof cover are connected as one piece. Step 4: Anchor Installation After assembling and inspecting the anchorages at both ends of the tower beam, temporarily fix the anchorages to the anchor plate. Step 5: Installation of the multi-hole reaction frame The perforated reaction frame includes a pressure plate, a support column, and a support plate. The pressure plate is supported on the support plate by the support column. The perforated reaction frame is installed at the tail of the anchor plate of the tower end anchor. The support plate is connected to the anchor plate. The pressure plate and the anchor plate are spaced apart and opposite to each other. The installation of the perforated reaction frame and the anchor plate is adjusted so that the hole arrangement on the pressure plate is consistent with the hole arrangement on the anchor plate. Step Six: Hoisting of the Outer Tubing Before threading the cable, the outer sleeve is hoisted to the pre-embedded pipe on the tower and its two ends are temporarily fixed to the tower and the beam, respectively. During the process, the extended steel strand is pulled into the tower end anchor and the beam end anchor and fixed. The extended steel strand passes through the outer sleeve and the tensioning of the extended steel strand will straighten the outer sleeve supported on it. Step 7: Threading and tensioning individual steel strands 7.1 Single cable threading using a high-tower cable threading machine Place the coiled steel strands from step two onto the lower cable reel on the upper tower. By pulling the first steel strand, rotate the cable reel and use the high tower cable threading machine to pull the steel strands to the top of the tower. The single steel strand passes through the wire-splitting wheel group of the high tower cable threading machine, and then uses the steel strand's own weight to thread it sequentially from the top of the tower → the inner cavity of the tower → the anchor at the tower end → the pre-embedded pipe inside the tower → the outer sleeve of the tower → the beam surface. The two steel strands are connected end to end to achieve continuous cable threading. After the first steel strand is lowered to the beam end and anchored in the anchor at the beam end, the two steel strands are disconnected at the tower end. Then, the first steel strand is tensioned. After the first steel strand is tensioned, the second steel strand is lowered from the anchor inside the tower for cable threading. 7.2 Tensioning of a single steel strand Tension each strand individually, using an electronic algorithm to calculate the force value of each strand to be at least 90% of the tension. The remaining tension is used as the average cable force. After tensioning all the strands of each cable, the uniformity of the cable force of each strand is checked, and the cable force is adjusted according to the remaining tension to make the tension of all the strands reach an average. Repeat steps 7.1 and 7.2 to complete the threading and tensioning of all the steel strands of one stay cable; Step 8: Secondary tensioning After completing the individual tensioning of all the steel strands of one stay cable in step seven, the entire bundle of steel strands of the stay cable is tensioned. The secondary tensioning is carried out in stages until 100% tension is achieved. After tensioning is completed, the exposed steel strands at the tower end and beam end are protected to prevent them from being exposed. Step 9: Clamping the top plate For low-stress anchorage of stay cables, to ensure anchorage reliability, after cable tension adjustment, the tension of a single steel strand will be less than 0.4σ. con The operation involves pressing the clamping plates with a jack. Step 10: Cut the steel strand to the desired length. After the main beam is closed, the cable tension is adjusted according to the monitoring instructions. After completion, the steel strands are cut according to the reserved length. The length of the steel strands should be adapted to the length of the protective cover, and the end of the steel strands should be 5-20mm away from the protective cover.

2. The method according to claim 1, characterized in that: In step one, one end of the traction steel wire rope is lowered from the manhole at the top of the tower to the anchor inside the tower, and the other end is passed through a pre-installed pipe outside the tower wall to the upper crossbeam or the place where the steel strands on the bridge deck are placed, and connected to the first extended steel strand. When the steel strand is pulled, the steel strand is raised to the cable-pulling machine of the high tower through the pipe.

3. The method according to claim 1, characterized in that: In step two, the steel strands are cut into sections on a wire feeding frame. The steel strands are supported by rollers. After the sleeves at both ends of each steel strand are removed, the center wire is upset. The center wire is tied near the upset head and the ends of two adjacent steel strands are connected by connectors. The entire roll of steel strands is protected during storage.

4. The method according to claim 1, characterized in that: In step four, the tower end anchorage includes an anchor plate, a support cylinder, a nut, and a tension end sealing cylinder. The anchor plate is located at the tail end of the support cylinder, the nut is screwed onto the outside of the support cylinder, the support cylinder is supported on the anchor plate, and the nut is tightly attached to the anchor plate. The beam end anchorage includes an anchor plate, a fixed end sealing cylinder, a washer, and an anchor plate. The washer is located at the tail end of the fixed end sealing cylinder and is welded to the fixed end sealing cylinder as a whole. A drainage groove is provided on one side of the washer, and the drainage groove is located below the washer. The side of the washer where the drainage groove is located is tightly attached to the anchor plate. Before the cable hanging construction, the anchor is pre-fixed to the anchor plate. After the nut or washer is tightly attached to the anchor plate, the anchor is temporarily fixed to the anchor plate.

5. The method according to claim 1, characterized in that: In step six, the outer sleeve is passed through the extension pipe and extends a certain length; temporary clamps are used to clamp the front and rear ends of the extension pipe; the outer sleeve is erected using roller frames and sleepers to prevent damage during movement; the outer sleeve is lifted by a tower crane and pre-installed on the bridge deck, then suspended from the outside of the tower by a hand-operated hoist; the extended steel strands are pulled into the anchorages inside the tower and the beam end anchorages respectively, and clamps are installed in the anchor holes of the anchorages to fix the extended steel strands; the extended steel strands are tensioned to straighten them.

6. The method according to claim 1, characterized in that: In step seven, in step 7.1, when the steel strand passes through the pre-embedded pipe opening inside the tower, it enters the cable guide pipe through the tower end anchorage using a guide pipe. At the outlet of the cable guide pipe outside the tower, an electric hoist is used as a construction platform for manual assistance in threading the outer sleeve pipe. When it reaches the beam end anchorage, the steel strand is threaded into the beam end anchorage using a traction rope.

7. The method according to claim 1, characterized in that: In step seven, specifically in step 7.1, during the process of threading the steel strands, the opening of the cable guide tube at the beam end and the port of the waterproof cover at the end of the HDPE outer sleeve are wrapped with a flexible tube; at the same time, when more than half of the steel strands have been threaded, the steel strands that have been threaded are bundled together, and the ends of the steel strands being threaded are wrapped to prevent them from crossing during the threading process.

8. The method according to claim 1, characterized in that: In step seven, in step 7.1, During the lowering of the steel strand, a metering device is set up to calculate the lowering length of the steel strand in order to control the speed and start / stop of the high tower cable threading machine. A meter-counting sensor is fixedly installed on the support of the high-tower cable-threading machine. Multiple sensing points are set on the circumference of the drum used for cable release. During the cable release process, the multiple sensing points periodically sense the meter-counting sensor during their circumferential stroke. The meter-counting sensor is connected to the control cabinet to calculate the cable release length. Construction personnel control the speed and start / stop of the high-tower cable-threading machine according to the cable release length.

9. The method according to claim 1, characterized in that: In step seven, specifically in step 7.2, to monitor the change in cable force of the steel strands during tensioning and to verify the tensioning accuracy, sensors are installed during construction to monitor the change in cable force of the first steel strand during the tensioning process of the subsequent steel strands. The readings of the sensors installed on the first steel strand are recorded and compared synchronously with the tensioning calculation values ​​calculated by the computer, thus achieving dual control of the calculation and actual tensioning process. To check the uniformity of cable tension, after the individual tensioning of all the strands of a stay cable is completed, several strands at different positions in the same cable bundle are selected and pulled out using jacks to obtain the hydraulic pressure value corresponding to the cable tension. If the test value exceeds the error range, the cable tension of each strand is averaged according to the remaining tension value.

10. The method according to claim 1 or 9, characterized in that: In step seven, following step 7.2, the tensioning of a single steel strand is performed at the tower end. The steps are as follows: a. Pass the top pressure rod through the steel strand and the perforated reaction frame, and put the top pressure sleeve on the top pressure rod; b. Pass the single-hole jack through the steel strand and press it against the top pressure sleeve to ensure that the groove of the jack piston head is fully embedded in the top pressure sleeve, i.e., the initial state is in place; c. Start the oil pump and use an electric algorithm to calculate the force value of each steel strand according to 90% of the tension force for tensioning. The remaining 10% of the tension force is used as the average cable force. d. When the tension reaches the calculated tension, stabilize the oil pressure and stop tensioning. Observe the scale on the jack or use a steel ruler to measure the piston stroke and record the value. e. Based on the recorded data, calculate the elongation of the steel strand and compare it with the theoretical value to see if it meets the allowable deviation. If it is within the deviation range, continue construction; otherwise, stop tensioning and check the cause. f. At the same time, observe whether the cable force value on the sensor matches the tension force. The cable force dispersion of a single strand should be within ±2%. If it exceeds the design allowable range, the cable force should be averaged and tensioned again according to the remaining 10% force value until the last steel strand is tensioned. When the sensor reading is within the allowable range of the design value, it can be ensured that the cable force error of the whole bundle is within ±1%. g. After all strands are tensioned, remove the single-hole anchor and sensor on the first strand, install the working clamp, and re-tension it with a single-hole jack so that the tensioning anchor force of the first strand is consistent with the reading of the last strand.

Images